1. Field
The field of the invention is retorting devices for removing mercury from ores and other mercury bearing materials.
2. Prior Art
The mercury-bearing material may be gold electrowinning sludge, Merrill-Crowe precipitate, smelter gas cleaning sludge, or any other material requiring removal of mercury. The material is commonly placed into an oven adapted for high temperature operation. The oven may be insulated in the interior on walls, top and door with mineral wool board or ceramic fiber cloth. The bottom may be insulated by fire brick or castable refractory material. Trays of the material are heated to volatilize the mercury, the resulting vapor then being directed through condensers, generally water cooled, to liquify the mercury vapor. The oven is subjected to vacuum to promote the volatilization of the mercury during the heating of the mercury bearing material.
Prior art retorting ovens are capable of operating temperatures of only 900.degree.-1100.degree. F., a temperature which does not thoroughly remove the mercury. Prior art mercury retorting ovens are unable to be operated under absolute pressures lower than 500-600 Torr, further limiting mercury removal. This is largely because the oven doors warp excessively at very high temperatures, breaking the oven vacuum seal. The oven and door frames are of common state of the art flange type components, which warp substantially at very high temperatures. Another shortcoming of prior art mercury retorting systems is that the mercury traps can only collect an unseparated mixture of the free mercury and other materials generally present in the condensate.
Therefore a need exists for an oven type retorting device which is capable of operating at much higher temperatures than presently available, in combination with lower operating pressures than are presently available, and that also incorporates an easily cleanable trap with provisions for separating the free mercury from any amalgams or sludge which may be condensed from oven gaseous effluent along with the mercury.